how to deselect other listBoxes when 1 is selected

I have 3 listBoxes and I want to deselect others when 1 of them is selected. How can I do this? I have tried setting the focused property to false, but c# doesn't allow assigning开发者_如何学运维 to the focused property.

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Assuming you have three list boxes, do the following. This code will clear the selection of every other list box when a particular list box changes selections. You can clear a list box selection by setting its SelectedIndex = -1.

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    if (listBox1.SelectedIndex > -1)
    {
        listBox2.SelectedIndex = -1;
        listBox3.SelectedIndex = -1;
    }
}

private void listBox2_SelectedIndexChanged(object sender, EventArgs e)
{
    if (listBox2.SelectedIndex > -1)
    {
        listBox1.SelectedIndex = -1;
        listBox3.SelectedIndex = -1;
    }
}

private void listBox3_SelectedIndexChanged(object sender, EventArgs e)
{
    if (listBox3.SelectedIndex > -1)
    {
        listBox1.SelectedIndex = -1;
        listBox2.SelectedIndex = -1;
    }
}

The if (listBox#.SelectedIndex > -1) is necessary because setting the SelectedIndex of a list box via code will also trigger its SelectedIndexChanged event, which would otherwise cause all list boxes to clear any time one of them was selected.

EDIT:

Alternatively, if you only have those three list boxes on your form, then you could consolidate it into one method. Link all three list boxes to this event method:

private void listBox_SelectedIndexChanged(object sender, EventArgs e)
{
    ListBox thisListBox = sender as ListBox;
    if (thisListBox == null || thisListBox.SelectedIndex == 0)
    {
        return;
    }

    foreach (ListBox loopListBox in this.Controls)
    {
        if (thisListBox != loopListBox)
        {
            loopListBox.SelectedIndex = -1;
        }
    }
}

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Using @Devin Burke's answer, so you don't have to worry having other controls in the form:

using System.Linq;
private void listBox_SelectedIndexChanged(object sender, EventArgs e)
{
    ListBox thisListBox = sender as ListBox;
    if (thisListBox == null || thisListBox.SelectedIndex == 0)
    {
        return;
    }

    foreach (ListBox loopListBox in this.Controls.OfType<ListBox>().ToList())
    {
        if (thisListBox != loopListBox)
        {
            loopListBox.SelectedIndex = -1;
        }
    }
}

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In my little NET5/Winforms app, the selected item of the current listbox won't stay blue/marked.

I found the solution for that is restoring focus back and set the index. Improving on the generic solution with a proper type check, Nane's answer,

    private void lbDefect_SelectedIndexChanged(object sender, EventArgs e) 
    {
       ListBox thisListBox = sender as ListBox;
       if (thisListBox == null || thisListBox.SelectedIndex == 0)
        {
          return;
        }
       var iSelected = thisListBox.SelectedIndex; // keep position..
       foreach (ListBox loopListBox in this.Controls.OfType<ListBox>().ToList())
       {
         if (thisListBox != loopListBox)
         {
           loopListBox.SelectedIndex = -1;
         }
       }
       // .. and this will show the selection for the current listbox
       thisListBox.Focus();
       thisListBox.SelectedIndex = iSelected;
    }